It is well known in the field of fiber optics that a damaged portion of a fiber optic cable will reflect at least a portion of the light traveling along the cable, back along the cable in a direction opposite the direction from which such light came. Using this phenomenon, optical time domain reflectometers (OTDR(s)) are able to locate damaged portions of fiber optic cables, at least to within a given range distance relative to known points along such cables. OTDRs typically operate by sending a very short-duration, high-power laser pulse along the optical cable, and by thereafter observing the returned reflections from the pulse. Although portions of the pulse are also reflected back by such things as connectors that are used to join individual sections of a fiber optic cable, by comparing the observed time domain reflection response to the time domain response that would be expected had the cable not been damaged, the portion of the pulse reflected by the damaged portion of the cable can be ascertained. The time delay between the emission of the laser pulse and the detection of its partial reflection back from the damaged portion of the cable can then be utilized to determine how far such light traveled, and hence the distance to the damaged portion.
The fiber optic cables are typically composed of long sections of clad fiber with connectors at either end to optically and mechanically couple one section of cable to the next and to connect the cable to fiber optic components (e.g. transmitters and receivers). These connectors are susceptible to damage, contamination, and other types of degradation. Depending on the type of degradation, the connector will either reflect or absorb, or both, an amount of electromagnetic energy (e.g. light) that would otherwise be transmitted through the connector. A connector that is contaminated with grease, for example, might exhibit mostly absorption. Another connector contaminated with a pollen grain(s) might exhibit some reflection as well as some absorption. An improperly seated connector might be almost entirely reflective. If the amount of energy absorbed or reflected is too great, the degradation causes the cable to fail. If instead the amount of energy is not enough to completely fail the cable, the degradation decreases the signal to noise ratio of the cable and, accordingly, limits the cable's bandwidth.
Thus, a need exists for improved methods of, and apparatus for, detecting and positively locating degraded fiber optic connectors.